I'm aware that the Personnel and Characters Dossier has a tab for persons of interest, but given how many different GoIs there are, it seems a little bare. Is there a resource I'm missing that goes into more detail about some of the more common faces in the GoIs? Are they on the individual GoI pages?

I think the reason is purely that we don't have too many common faces.

Like, there's Vince Anderson, for Anderson's Robotics, and everyone he works with. There's the Black Queen. I think Robert Bumaro shows up a bit.

Then there's various, author-specific tales and interconnected pieces, which tend to stay isolated in their own little sections of the wiki. But elements common to specific organizations tend to be more in the area of motifs and ideas and group structures; generally people are relegated to a more personal role for the author. I think someone described it once as 'playing with someone else's toys' - which I guess would be true in general. Maybe it just feels strange.

Hence is the (relative) dearth for general-purpose, interesting characters across multiple universes. It's been a factor of the wiki for a while, and iirc the page you linked was part of an effort to crack down on that kind of stuff. Promoting character-based creativity, etc.. idk how well it's worked.

After reading some of the discussion page1 on the Character essay, I stumbled upon this comment:

Want to introduce a pope like [sic] figure to the church of the broken god? Unless you pull out an absolutely amazing piece of writing, everybody decries it as you trying to enforce your ideas on the canon.

which, when combined with the page being older than I first assumed, tells me that the site as a whole seems to generally agree with your "playing with someone else's toys" assessment. While deviations within GoIs can be explained away as splinter groups, deviations from established characters are much harder to handwave. Its just kind of a shame, because I would love some more recognizable faces to play with, but I understand why the sentiment exists.

Footnotes

1. Okay so it's the very first comment but it immediately addressed this so I stopped combing